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推波板制造双频波数值模拟
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作者 李海涛 《科技资讯》 2015年第15期245-245,247,共2页
该文应用软件为FLUENT流体分析软件,控制方程为连续性方程和Navie r-Stokes方程。应用GAMBIT建主数值波浪水槽模型并对其划分网格。基于标准RNG湍流模型和VOF自由液面捕捉方法,利用FLUENT的二次开发编写源程序,赋予前边界造波功能,以及... 该文应用软件为FLUENT流体分析软件,控制方程为连续性方程和Navie r-Stokes方程。应用GAMBIT建主数值波浪水槽模型并对其划分网格。基于标准RNG湍流模型和VOF自由液面捕捉方法,利用FLUENT的二次开发编写源程序,赋予前边界造波功能,以及后边界数值消波功能,采用动网格来实现推波板单频造波。其与实际物理实验造波原理相符。并在此基础上,以stokes有限振幅波理论为基本理论,运用二阶双色波的推波板运动方程实现非线性双频波造波数值模拟。 展开更多
关键词 FLUENT 动网格 推波板 造波 双频波
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A Dual-polarized Frequency Selective Rasorber with a Tunable Transparent Band
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作者 SHI Tongtong ZHANG Xiaofa +4 位作者 WU Weiwei WANG Shaozhi XU Yixuan YAN Yuchen YAN Xiao 《电讯技术》 北大核心 2024年第10期1569-1575,共7页
A tunable dual polarization absorption-transmission-absorption(A-T-A)frequency selective absorbers(FSR)to address the issue of high insertion loss in current tunable FSRs is proposed.The lumped resistors are loaded on... A tunable dual polarization absorption-transmission-absorption(A-T-A)frequency selective absorbers(FSR)to address the issue of high insertion loss in current tunable FSRs is proposed.The lumped resistors are loaded onto the lossy layer to absorb electromagnetic waves within the absorption band.The varactor diodes are loaded onto another lossless layer to control the transmission frequency band of the FSR.Its equivalent circuit model is provided.The proposed tunable FSR can change the passband within the range of 14.5~15.5 GHz by changing the bias voltage applied to the lossless transmission layer,while maintaining insertion loss above-1.67 dB.The series resonant structure of the lossy layer generates bilateral absorption bands between 10.2~13.5 GHz and 17.2~22 GHz,with broadband reflection suppression ranging from 10.3 GHz to 22 GHz(70.7%).The prototype is manufactured,and the measured results have verified the simulation results. 展开更多
关键词 tunable frequency selective rasorber DUAL-POLARIZATION RCS reduction stealthy radomes
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电场激励法超前探测原理及仪器发射部分研制
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作者 张伟杰 罗建国 +1 位作者 胡兴志 孙辉辉 《华北科技学院学报》 2016年第1期81-85,共5页
为了丰富和提高煤矿巷道电法超前探测的手段和效率,利用煤岩激发极化和电场同性相斥的基本性质,分析在双频激电电流作用下的约束电场的百分频率效应,得出前方围岩特性来间接判断地质异常。所研制的超前探测仪发射部分采用整流隔离稳压... 为了丰富和提高煤矿巷道电法超前探测的手段和效率,利用煤岩激发极化和电场同性相斥的基本性质,分析在双频激电电流作用下的约束电场的百分频率效应,得出前方围岩特性来间接判断地质异常。所研制的超前探测仪发射部分采用整流隔离稳压和模块化设计,示波器得到的发射电流波形为双频波,强度可方便调节,达到了设计要求。 展开更多
关键词 电场激励法 超前探测 百分频率效应 隔离稳压 双频波
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Integrated interpretation of dual frequency induced polarization measurement based on wavelet analysis and metal factor methods 被引量:2
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作者 韩世礼 张术根 +2 位作者 柳建新 胡厚继 张文山 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2013年第5期1465-1471,共7页
In mineral exploration, the apparent resistivity and apparent frequency (or apparent polarizability) parameters of induced polarization method are commonly utilized to describe the induced polarization anomaly. When... In mineral exploration, the apparent resistivity and apparent frequency (or apparent polarizability) parameters of induced polarization method are commonly utilized to describe the induced polarization anomaly. When the target geology structure is significantly complicated, these parameters would fail to reflect the nature of the anomaly source, and wrong conclusions may be obtained. A wavelet approach and a metal factor method were used to comprehensively interpret the induced polarization anomaly of complex geologic bodies in the Adi Bladia mine. Db5 wavelet basis was used to conduct two-scale decomposition and reconstruction, which effectively suppress the noise interference of greenschist facies regional metamorphism and magma intrusion, making energy concentrated and boundary problem unobservable. On the basis of that, the ore-induced anomaly was effectively extracted by the metal factor method. 展开更多
关键词 dual frequency induced polarization method wavelet analysis metal factor Arabian-Nubian shield volcanogenic massive sulfide deposit
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Phase estimation in bispectral domain based on conformal mapping and applications in seismic wavelet estimation 被引量:8
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作者 Yu Yong-Cai Wang Shang-Xu +1 位作者 Yuan San-Yi Qi Peng-Fei 《Applied Geophysics》 SCIE CSCD 2011年第1期36-47,95,共13页
Seismic wavelet estimation is an important part of seismic data processing and interpretation, whose preciseness is directly related to the results of deconvolution and inversion. Wavelet estimation based on higher-or... Seismic wavelet estimation is an important part of seismic data processing and interpretation, whose preciseness is directly related to the results of deconvolution and inversion. Wavelet estimation based on higher-order spectra is an important new method. However, the higher-order spectra often have phase wrapping problems, which lead to wavelet phase spectrum deviations and thereby affect mixed-phase wavelet estimation. To solve this problem, we propose a new phase spectral method based on conformal mapping in the bispectral domain. The method avoids the phase wrapping problems by narrowing the scope of the Fourier phase spectrum to eliminate the bispectral phase wrapping influence in the original phase spectral estimation. The method constitutes least-squares wavelet phase spectrum estimation based on conformal mapping which is applied to mixed-phase wavelet estimation with the least-squares wavelet amplitude spectrum estimation. Theoretical model and actual seismic data verify the validity of this method. We also extend the idea of conformal mapping in the bispectral wavelet phase spectrum estimation to trispectral wavelet phase spectrum estimation. 展开更多
关键词 conformal mapping higher-order spectra phase wrapping wavelet estimation
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A quantitative analysis method for GPR signals based on optimal biorthogonal wavelet 被引量:6
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作者 LIU Hao-ran LING Tong-hua +2 位作者 LI Di-yuan HUANG Fu ZHANG Liang 《Journal of Central South University》 SCIE EI CAS CSCD 2018年第4期879-891,共13页
Due to the disturbances arising from the coherence of reflected waves and from echo noise,problems such as limitations,instability and poor accuracy exist with the current quantitative analysis methods.According to th... Due to the disturbances arising from the coherence of reflected waves and from echo noise,problems such as limitations,instability and poor accuracy exist with the current quantitative analysis methods.According to the intrinsic features of GPR signals and wavelet time–frequency analysis,an optimal wavelet basis named GPR3.3 wavelet is constructed via an improved biorthogonal wavelet construction method to quantitatively analyse the GPR signal.A new quantitative analysis method based on the biorthogonal wavelet(the QAGBW method)is proposed and applied in the analysis of analogue and measured signals.The results show that compared with the Bayesian frequency-domain blind deconvolution and with existing wavelet bases,the QAGBW method based on optimal wavelet can limit the disturbance from factors such as the coherence of reflected waves and echo noise,improve the quantitative analytical precision of the GPR signal,and match the minimum thickness for quantitative analysis with the vertical resolution of GPR detection. 展开更多
关键词 GPR detection signal quantitative analysis wavelet time–frequency analysis biorthogonal wavelet basis
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EXPERIMENTAL STUDY ON SOIL MOISTURE USING DUAL-FREQUENCY MICROWAVE RADIOMETER 被引量:2
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作者 GUAN Zhi ZHAO Kai SONG Dong-sheng 《Chinese Geographical Science》 SCIE CSCD 2006年第1期83-86,共4页
An experiment of measuring soil moisture was carried out by using dual-frequency microwave radiometer designed by the authors. The measured data were analyzed by using statistical regression method and the empirical r... An experiment of measuring soil moisture was carried out by using dual-frequency microwave radiometer designed by the authors. The measured data were analyzed by using statistical regression method and the empirical regression model of retrieving soil moisture in L-band and C-band was developed. The soil moisture in a rainfall event was retrieved using the experiential regression model, which is consistent well with the field sampling value. The results show that when soil moisture is lower than 75%, the brightness temperature is linear with soil moisture. However, when soil moisture is higher than 75%, the brightness temperature is not linear with soil moisture, so it is difficult for microwave radiometer to measure the changes of soil moisture. The experiment verifies the effectiveness and feasibility of microwave remote sensing soil moisture. Although this method for linear regression based on the data measured with the radiometer is simple, and has strong adaptability, generally it has only local application value, and lacks universal applicability for different areas and different conditions. 展开更多
关键词 soil moisture dual-frequency microwave radiometer brightness temperature
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Unified Form of Photorefractive Coupling-wave Equation in the Undepleted Pump Approximate and the Lossless Solution
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作者 LIU Jinsong LIANG Changhong(Xidian University,Xi’an 710071,CHN) 《Semiconductor Photonics and Technology》 CAS 1996年第2期108-111,共4页
The coupling-wave equations of photorefractive wave mixing processes including two-and four-wave mixing are expressed as an unified matrix equation in the undepleted pump approximation.The lossless general solution of... The coupling-wave equations of photorefractive wave mixing processes including two-and four-wave mixing are expressed as an unified matrix equation in the undepleted pump approximation.The lossless general solution of the matrix equation is obtained.The previous formulas of five wave-mixing processes in the undepleted pump are derived from the solution when their boundary conditions are used. 展开更多
关键词 Photorefractive Effects Two-wave-mixing Four-wave Mixing
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Temperature Dependence of Thermal Emission Rate in Cr: GaAs
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作者 LIU Jinsong LIANG Changhong(Xidian University, Xi’an 710071, CHN ) 《Semiconductor Photonics and Technology》 CAS 1996年第3期180-183,共4页
The new method of measuring the ratio of thermal emission rate to the photoexcitation constant is presented. The temperature dependence of the ratio for Cr:GaAs is calculated by using the previously published data of ... The new method of measuring the ratio of thermal emission rate to the photoexcitation constant is presented. The temperature dependence of the ratio for Cr:GaAs is calculated by using the previously published data of two-wave mixing. Results show that the calculating data and previous phenomenological theoretic ones coincide with each other very well. 展开更多
关键词 Photorefractive Effect Thermal Emission Rate Two-wave Mixing
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A Wide-Spaced Dual-Band Metamaterial Absorber Based on 2.5D Frequency Selective Surfaces and Magnetic Material
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作者 DENG Junyu LIU Shaobin +1 位作者 LI Wei WU Chen 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2021年第5期800-806,共7页
By applying meander-line for electrical loss and magnetic material for magnetic loss,we present a metamaterial absorber which is wide-spaced and dual-band(1.35—2.24 GHz and 10.37—12.37 GHz).The novelty of this study... By applying meander-line for electrical loss and magnetic material for magnetic loss,we present a metamaterial absorber which is wide-spaced and dual-band(1.35—2.24 GHz and 10.37—12.37 GHz).The novelty of this study mainly lies in a combination of two kinds of losses to consume electromagnetic energy,which can get better dual-band absorption.In the electrical loss layer,meander-line structures are printed on both surfaces of the substrate and the structure series with resistors.Considering the need for miniaturization,we connect eight metallic vias with these meander-line areas to form a compact 2.5-dimensional(2.5D)structure.The dimension of the unit cell is miniaturized to be 5.94 mm×5.94 mm,about 0.035λat the center frequency of the lower absorption band.In the magnetic loss layer,the 0.4 mm thick magnetic material is employed on a metallic ground plane.In addition,the complex permittivity and complex permeability of the magnetic material are given.Finally,we fabricate a prototype of the proposed absorber and obtain a measurement result which is in good agreement with the full-wave simulation result. 展开更多
关键词 metamaterial absorber DUAL-BAND frequency selective surfaces magnetic material
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Intensity Dependence of Stationary Energy Transfer in Codirectional Photorefractive Two-wave Mixing
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作者 LIU Jinsong LIANG Changhong(Xidian University, Xi’an 710071, CHN ) 《Semiconductor Photonics and Technology》 CAS 1996年第1期37-41,共5页
The intensity and phase formulas that are valid for the saturation and intermediate regime (before saturation) are derived, and the analytical expressions with the ratio of saturation intensity to total incident inten... The intensity and phase formulas that are valid for the saturation and intermediate regime (before saturation) are derived, and the analytical expressions with the ratio of saturation intensity to total incident intensity as their explicit variable are obtained. The intensity dependence of stationary energy transfer in photorefractive codirectional two-wave mixing is examined. It is necessary to using these formulas in some problems, such as the temperature or intensity dependence of two-wave mixing. A method of measuring exponential gain coefficient is presented, which is suitable for two-wave mixing in intermediate regime. 展开更多
关键词 Photorefractive Effects Two-wave Mixing Intensity Dependence
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An adaptive preprocessing algorithm for low bitrate video coding
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作者 LI Mao-quan XU Zheng-quan 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2006年第12期2057-2062,共6页
At low bitrate, all block discrete cosine transform (BDCT) based video coding algorithms suffer from visible blocking and ringing artifacts in the reconstructed images because the quantization is too coarse and high f... At low bitrate, all block discrete cosine transform (BDCT) based video coding algorithms suffer from visible blocking and ringing artifacts in the reconstructed images because the quantization is too coarse and high frequency DCT coefficients are inclined to be quantized to zeros. Preprocessing algorithms can enhance coding efficiency and thus reduce the likelihood of blocking artifacts and ringing artifacts generated in the video coding process by applying a low-pass filter before video encoding to remove some relatively insignificant high frequent components. In this paper, we introduce a new adaptive preprocessing algo- rithm, which employs an improved bilateral filter to provide adaptive edge-preserving low-pass filtering which is adjusted ac- cording to the quantization parameters. Whether at low or high bit rate, the preprocessing can provide proper filtering to make the video encoder more efficient and have better reconstructed image quality. Experimental results demonstrate that our proposed preprocessing algorithm can significantly improve both subjective and objective quality. 展开更多
关键词 Blocking artifact Quantization parameter Video preprocessing Bilateral filtering
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Selective image enhancement method for low energy target information area
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作者 朱利 陈继锋 +1 位作者 秦辰 曾明 《Journal of Central South University of Technology》 EI 2006年第5期563-567,共5页
A selective subband enhancement method based on biorthogonal wavelet base is proposed. This novel image enhancement method is just for those images in which the energy of target information area is relatively lower. I... A selective subband enhancement method based on biorthogonal wavelet base is proposed. This novel image enhancement method is just for those images in which the energy of target information area is relatively lower. It includes two parts: one is enhancing the low frequency subband by wavelet decomposition and the other is building a new criterion based on entropy window to image evaluation. Experimental results show that this new scheme may result in a perfect image processing. 展开更多
关键词 wavelet transform biorthogonal wavelet basel selective subband enhancement entropy windowl lowfrequency subband
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Dual-band multi-beam reconfigurable terahertz antenna based on graphene frequency selective surface
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作者 JIN Zhao RONG Yu +4 位作者 QIAO Li-Ping YU Jing-Dong WU Fei GUO Chen TIAN Dou 《红外与毫米波学报》 SCIE EI CAS 2024年第5期628-633,共6页
In this paper,a dual-band graphene-based frequency selective surface(GFSS)is investigated and the operating mechanism of this GFSS is analyzed.By adjusting the bias voltage to control the graphene chemical po-tential ... In this paper,a dual-band graphene-based frequency selective surface(GFSS)is investigated and the operating mechanism of this GFSS is analyzed.By adjusting the bias voltage to control the graphene chemical po-tential between 0 eV and 0.5 eV,the GFSS can achieve four working states:dual-band passband,high-pass lowimpedance,low-pass high-impedance,and band-stop.Based on this GFSS,a hexagonal radome on a broadband omnidirectional monopole antenna is proposed,which can achieve independent 360°six-beam omnidirectional scanning at 1.08 THz and 1.58 THz dual bands.In addition,while increasing the directionality,the peak gains of the dual bands reach 7.44 dBi and 6.67 dBi,respectively.This work provides a simple method for realizing multi-band terahertz multi-beam reconfigurable antennas. 展开更多
关键词 THz antenna multi-beam graphene dual-band reconfigurable
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Dual-band bandpass tunable microwave photonic filter based on stimulated Brillouin scattering 被引量:3
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作者 李嘉琪 肖永川 +1 位作者 董玮 张歆东 《Optoelectronics Letters》 EI 2016年第4期276-279,共4页
A dual-band bandpass microwave photonic filter(MPF) based on stimulated Brillouin scattering(SBS) is theoretically analyzed and experimentally demonstrated. Two separated tunable laser sources(TLSs) are employed to ge... A dual-band bandpass microwave photonic filter(MPF) based on stimulated Brillouin scattering(SBS) is theoretically analyzed and experimentally demonstrated. Two separated tunable laser sources(TLSs) are employed to generate two passbands by implementing phase modulation to amplitude modulation conversion by using SBS induced sideband amplification. The center frequencies of both passbands can be independently tuned ranging from 1 GHz to 19 GHz. High resolution with 3 d B bandwidth less than 30 MHz and large out-of-band rejection about 40 d B under 25 m W optical pump power are achieved. 展开更多
关键词 Bandpass filters Brillouin scattering Microwave filters MODULATION Optical pumping Phase modulation Surveying instruments
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A compact dual-band bandpass filter based on porous silicon dual-microcavity of one-dimensional photonic crystal
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作者 马辉 张红燕 《Optoelectronics Letters》 EI 2015年第2期95-99,共5页
We propose a compact dual-band bandpass filter(BPF)based on one-dimensional porous silicon(PS)photonic crystal by electrochemical etching.By inserting three periods of high and low reflective index layers in the cente... We propose a compact dual-band bandpass filter(BPF)based on one-dimensional porous silicon(PS)photonic crystal by electrochemical etching.By inserting three periods of high and low reflective index layers in the center of porous silicon microcavity(PSM),two sharp resonant peaks appear in the high reflectivity stop band on both sides of the resonance wavelength.Through simulation and experiment,the physical mechanisms of the two resonance peaks and the resonance wavelength are also studied.It is found that the resonance wavelength can be tuned only by adjusting the effective optical thickness(EOT)of each PS layer,in which different resonance wavelengths have different widths between the two sharp resonance peaks.Besides,the analysis indicates that oxidization makes the blue shift become larger for high wavelength than that for low wavelength.Such a fabricated BPF based on PS dual-microcavity is easy to be fabricated and low cost,which benefits the application of integrated optical devices. 展开更多
关键词 Bandpass filters MICROCAVITIES Photonic crystals RESONANCE Silicon
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